1. Field of the Invention
This invention generally relates to displacement transducers, and, more specifically, to high sensitivity displacement transducers for MEMS and NEMS
2. Background
A displacement transducer is a device which senses displacement of an object, and, responsive thereto, provides an electrical signal representative of the displacement of the object. Known displacement transducers sense macro-level displacements. However, these transducers are not readily scaleable to micro-or nano-scale dimensions, although many applications exist for micro-or nano-level displacement transducers. System-level applications for such transducers are generally referred to as micro-electro-mechanical systems (MEMS) or nano-electro-mechanical transducers (NEMS). Consequently, there is an unmet need for micro-or nano-scale displacement transducers.
In accordance with one aspect of the invention, there is provided a displacement transducer in which a movable mechanical element is mounted through at least one anchor point to a substrate. The element is mounted in close proximity to a Hall sensor. The Hall sensor has a Hall junction which is linked to magnetic flux emanating from the magnet integrated into the mechanical element. A force is exerted on the mechanical element, causing displacement of the magnet. The displacement of the magnet causes a change in the magnetic flux linked to the Hall junction. The change in magnetic flux linked to the Hall junction induces a change in the voltage potential across the Hall junction. One or more signal lines are coupled to the Hall junction. A signal is output on these signal lines which is representative of the change in transverse voltage across the Hall junction.
In one implementation, the mechanical element is a diamond-shaped torsional resonator mounted to the substrate at first and second anchor points. A thin film magnet is integrated into the resonator. When a force is exerted on the resonator, vertical displacement, either upwards or downwards, of the ends of the magnet is achieved.
The Hall sensor in this implementation is a four-terminal semiconductor Hall sensor which is also anchored to the substrate. Two of the terminals are current terminals coupled together through a Hall junction. The other two terminals are voltage terminals coupled to either side of the Hall junction. The terminals are in a folded cross-shaped configuration to facilitate placement of the Hall junction in close proximity to the magnet. That allows a greater amount of magnetic flux emanating from the magnet to be linked to the Hall junction, thereby increasing the sensitivity of the transducer.
Other implementations are possible in which the mechanical device is formed of a flexural device such as a suspended cantilever or suspended beam into which a micro-or nano-scale magnet is incorporated. Moreover, an equivalent embodiment is possible in which the Hall sensor is integrated within a mechanical element which is anchored to the substrate in close proximity to a stationary micro-or nano-scale magnet.